Although considered a modifiable risk factor for coronary artery disease (CAD) in the general population, the magnitude of physical activity required to promote cardiorespiratory fitness and a clinically meaningful change in blood-derived biomarkers of CAD is not achievable in those with a severe physical disability, such as with immobilizing paralysis from spinal cord injury (SCI). During the chronic phase of SCI, a characteristic dyslipidemia emerges, with mean serum high density lipoprotein cholesterol (HDL-C) concentrations \<40 mg/dl, a threshold level for HDL-C that is appreciated to be an independent risk factor for CAD, elevations in triglycerides (TG) to concentrations at, or near, target values for the general population that trigger clinical intervention, and low density lipoprotein cholesterol (LDL-C) concentrations that are within the normal range. It should not be a surprise that cardiovascular disease (CVD)-related morbidity in persons with SCI occurs earlier in life, at a greater prevalence than that of the general population, and is the primary cause of death after the first year of injury. Population-based epidemiological studies are unavailable for clinical guidance because of the relatively low incidence rates for SCI. Clinical target values used to initiate treatment in the general population may be inappropriate in those with SCI because of their unique pathophysiology. In the absence of significant physical activity and lifestyle modifications, it would seem that appropriate pharmaceutical options are needed to properly manage markers of CVD-related risk in persons with SCI. To date, there is limited empirical evidence to support the use of lipid-lowering treatments in persons with SCI.
Fenofibrate is a fibric acid derivate that activates peroxisome proliferator-activated receptor and lipoprotein lipase, leading to enhanced elimination of TG from plasma. In clinical trials where fenofibrate was used as a monotherapy, serum TG concentrations fell 41-53%, very low density lipoprotein (VLDL) fell 38-52%, LDL-C decreased 6-20%, and HDL-C improved by as much as 20%. In consideration for the nature of dyslipidemia in persons with SCI, fenofibrate appears to be an appropriate first-line agent for treatment in this cohort, especially because most of those with SCI have LDL values that are within the clinically acceptable range. In the general population, standard clinical practice for lipid-lowering treatment with fenofibrate monotherapy follows a known and clinically accepted timeline to monitor safety and to determine therapeutic efficacy. It is recommended that, if after 2 months of continuous therapy there are no beneficial changes to the lipoprotein profile, that treatment be discontinued (i.e., non-responders). Similarly, several large clinical trials have demonstrated that the peak therapeutic effects of fenofibrate are observed after 12-16 weeks of treatment (i.e., responders). The proposed study will test the efficacy of administering fenofibrate to persons with SCI, a severely immobilized cohort that does not have established clinical practice guidelines to treat dyslipidemia and appears to have unique considerations that may be hypothesized to call for a more disease-specific approach for care. If successful, the treatment will reduce clinical markers of CVD-related risk by modifying the concentration and number of particles that are known to contribute to incident cardiac events and mortality. It is anticipated that the insight gained from this investigation will provide clinicians with a proof-of-concept for instituting appropriate use of lipid lowering agents to treat the dyslipidemia that has been well described in persons with SCI.
